The present invention relates to a method and apparatus for manipulating sheets which consist of paper or the like. More particularly, the invention relates to a method and apparatus for converting a series of discrete sheets into a so-called scalloped stream wherein a portion of each next-following sheet overlies a portion of the preceding sheet. Still more particularly, the invention relates to improvements in a method and in an apparatus of converting successive satisfactory sheets of a series of randomly distributed saitsfactory and unsatisfactory sheets into a scalloped stream between a cross cutter, which subdivides a single continuous running web or two or more overlapping running webs into a file of discrete sheets or groups of overlapping sheets, and a stacking station where the scalloped stream is converted into a succession of stacks of overlapping satisfactory sheets.
The making of a scalloped stream of partially overlapping sheets involves the transport of non-overlapping sheets or groups of sheets at a higher first speed and subsequent deceleration of successive sheets or groups of sheets to a lower second speed. As a rule, discrete sheets or discrete groups of overlapping sheets are obtained by drawing one or more webs from discrete reels or bobbins and advancing such webs through a cross cutter which severs the web or webs at regular intervals. The stacking of sheets is preceded by their conversion into a scalloped stream. This involves a deceleration or braking of successive sheets in a portion of their path between the cross cutter and the stacking station. The deceleration normally involves propulsion of the leaders of successive rapidly advancing sheets against the peripheral surface of a relatively slow braking or decelerating roller or drum with attendant reduction of speed and conversion of the series of sheets into a scalloped stream.
The above outlined technique of forming a scalloped stream is satisfactory as long as the series of discrete sheets consists of satisfactory sheets, i.e., as long as all of the sheets which constitute the series are disposed at the same distance from each other. This is not the case when the unsatisfactory sheets are segregated from satisfactory sheets between the cross cutter and the decelerating station. The segregation of one or more unsatisfactory sheets entails the development of longer gaps between certain satisfactory sheets, namely between the leader of a satisfactory sheet which follows one or more segregated unsatisfactory sheets and the trailing end of the preceding satisfactory sheet. If the sheets are advanced at an elevated speed, the foremost satisfactory sheet following one or more segregated unsatisfactory sheets is likely to advance past the braking or decelerating means without any deceleration and to create irregularities in the scalloped stream. This means that it is necessary to intervene into the automatic formation of the scalloped stream in order to reestablish the optimum conditions at the decelerating station. Each such intervention involves a reduction of the output and necessitates a continuous monitoring of the machine.